Statutory Accounting and Dividend Restrictions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Aflac
Statutory Accounting Practices [Line Items]
Net Income, Nebraska state basis	$ 444	$ 1,500	$ 1,400
Capital and surplus, statutory accounting practices of the state or country basis	6,371	6,740
Net assets, GAAP basis	15,814	12,902
Amount available for dividend distribution without prior approval from regulatory agency	637
Dividends declared	282
Aflac | Separate Account Funding Agreements
Statutory Accounting Practices [Line Items]
Guaranteed separate account funding agreements, unrealized gain (loss)	45	(113)
Aflac Japan
Statutory Accounting Practices [Line Items]
Capital and surplus, statutory accounting practices of the state or country basis	2,700	2,300
Net assets, GAAP basis	$ 10,998	$ 8,907
Net assets of Aflac Japan as a percentage of aggregated GAAP basis net assets of insurance subsidiaries	69.10%	68.50%